Proposal

Policy Proposal 2005-9: 4-Byte AS Number

Policy statement:

This policy proposal nominates 3 dates for changes to the current AS Number
allocation policy for the registry:

- Commencing 1 January 2007 the registry will process applications that
specifically request 32-bit only AS Numbers and allocate such AS numbers
as requested by the applicant. In the absence of any specific request for
a 32-bit only AS Number, a 16-bit only AS Number will be allocated by the
registry.

- Commencing 1 January 2009 the registry will process applications that
specifically request 16-bit only AS Numbers and allocate such AS Numbers
as requested by the applicant. In the absence of any specific request for
a 16-bit only AS Number, a 32-bit only AS Number will be allocated by the
registry.

- Commencing 1 January 2010 the registry will cease to make any distinction
between 16-bit only AS Numbers and 32-bit only AS Numbers, and will operate
AS number allocations from an undifferentiated 32-bit AS Number allocation
pool.

Terminology

"16-bit only AS Numbers" refers to AS numbers in the range 0 -
65535

"32-bit only AS Numbers" refers to AS Numbers in the range 65,536 - 4,294,967,295

"32-bit AS Numbers" refers to AS Numbers in the range 0 - 4,294,967,295

Rationale:

Recent studies of AS number consumption rates indicate that the existing
16-bit pool of unallocated AS Numbers will be exhausted sometime in the
period between 2010 and 2016, absent of any concerted efforts of recovery
of already-allocated AS Numbers [1] [2]. Standardization work in the IETF
has produced a document that is currently being submitted as a Proposed
Standard that will expand the AS Number space to a 32-bit field [3].

It is noted that some advance period may be required by network operators
to undertake the appropriate procedures relating to support of 32-bit AS
numbers, and while no flag day is required in the transition to the longer
AS Number field, it is recognised that a prudent course of action is to
allow for allocation of these extended AS numbers well in advance of an
anticipated 16-bit AS Number exhaustion date.

This policy proposal details a set of actions and associated dates for RIR
AS Number allocation policies to assist in an orderly transition to use
of the 32-bit AS Number space.

The essential attributes of this policy proposal are to facilitate the ease
of transitional arrangements by equipment vendors, network managers and
network operations staff, to provide the industry with some predictability
in terms of dates and associated actions with respect to registry operational
procedures for AS Number allocations.

References

[1] Daily AS Number Report, http://www.potaroo.net/tools/asns
[2] ASNs MIA: A Comparision of RIR Statistics and RIS Reality, http://www.nanog.org/mtg-0510/wilhelm.html
[3] BGP Support for Four-octet AS Number Space, draft-ietf-idr-as4bytes-12.txt

Timetable for implementation: Procedures to support this proposal need to
be implemented by 1 January 2007